I have a WPF ItemsControl who's ItemsSource is bound to an observable collection of view models in MVVM. The ItemTemplate is set to the user control that I want. However, there are instances when I would like another control instead of the one specified in XAML.
How can I easily do this?
Use DataTemplates to map view models to views:
<ItemsControl ItemsSource="{Binding SomeCollectionOfViewModels}">
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type local:FirstViewModel}">
<Label>Foo</Label>
</DataTemplate>
<DataTemplate DataType="{x:Type local:SecondViewModel}">
<Label>Bar</Label>
</DataTemplate>
</ItemsControl.Resources>
</ItemsControl>
If I understand you have a collection that contains two different type of object and you want 2 different template.
You could build a datatemplate for each object type and leave WPF to render the right template based on the object type.
Related
I know this question has been asked and answered several times already but I still don't get it. I seem to be missing a piece of understanding.
I have a TabControl bound to an observable list of viewmodels. The viewmodels can be of different types, derived from the same base type, of course. When a viewmodel is added to the list I want the tabcontrol adds a new tabpage based on the type of the view model.
I do not understand how to set up the ContentTemplate of the TabControl to pick the right view based on the type of the view model.
A Basic example can be found here, but I do not get it up and running with dynamic views:
How to bind items of a TabControl to an observable collection in wpf?
Thanks! Johannes
Ok, i will modify the sample code in the answer you linked:
<Window.Resources>
<DataTemplate x:Key="templateForTheHeader" DataType="{x:Type vm:BaseViewModel}">
<TextBlock Text="{Binding CommonPropertyToDisplayInTheHeader}"/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:ViewModel1}">
<TextBlock Text="{Binding PropertyInVM1}"/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:ViewModel2}">
<TextBlock Text="{Binding PropertyInVM2}"/>
</DataTemplate>
</Window.Resources>
...
<TabControl ItemsSource="{Binding YourCollection}"
ItemTemplate="{StaticResource templateForTheHeader}">
</TabControl>
The header displays some property in the base VM class.
And the important thing, i removed the x:key of the other DataTemplates, this will make it being applied to every instance of the defined DataType found in the Window (ContentTemplate in the TabControl not needed).
YourCollection is a mix of objects, each of it will get its template applied based on its type if a DataTemplate with matching DataType exists. Simple uh?
I am developing a custom WPF control and confused how to use the dependency property. My view model contains 2 properties:
class Customer {
string Name;
string ID;
}
My custom control is responsible for displaying these fields.
Q1: Do I need to define any dependency properties (eg "Name", "ID") in my custom control?
Q2: I am using ItemsControl to display a list of Customers. How is the Customer object passed to my custom control? Is it done through the DataContext or do I need to add a "Customer" dependency property in my control and in the xaml, bind "Customer" to "something" (what's that something)?
<ItemPresenter>
<MyCustomControl Customer="??what should i put here???"/>
</ItemPresender>
Q1. Why do you have a custom control? Ordinarily, you would just create a UserControl (there is a distinction in WPF between UserControl and custom control) and bind properties within your UserControl to properties of your view model. For example (let's call this CustomerView):
<UserControl ...>
<StackPanel>
<TextBlock Text="{Binding ID}"/>
<TextBox Text="{Binding Name}"/>
</StackPanel>
</UserControl>
Q2. Through the DataContext. For example, you might have something like this:
<ItemsControl ItemsSource="{Binding Customers}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<local:CustomerView/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Each item generated by the ItemsControl will have the related data item set as its DataContext. Hence, each CustomerView will have the appropriate Customer as its DataContext.
I'm learning the ins and outs of creating custom controls in WPF. The concepts I understand thus far:
The code defines the control's behavior.
The template defines the control's look and feel, the visual aspect.
You can bind elements of the template to properties of the underlying control object.
If the template has multiple collection controls, such as StackPanels, how do you bind them so that they are populated by underlying collections? My first inclination was to make use of the DataContext of each StackPanel, but I couldn't make it work. I get the feeling I'm missing a key concept that would solve this for me.
What did you want to be in these StackPanels? Panels are used for arranging items. If you want to show a collection of items, you probably want to be using an ItemsControl (or one of the many types of ItemsControls). An ItemsControl is very powerful- you can specify how the items are displayed and how the panel that they're displayed on is displayed as well. You can even specify that the panel is a StackPanel. For example,
<ItemsControl ItemsSource="{Binding ElementName=root, Path=List1}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<!-- Template defines the panel -->
<StackPanel IsItemsHost="True" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<!-- Template defines each item -->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Then you wanted to bind to a list of items, which is very easy with an ItemsControl! In your case with the custom control, you may want to expose dependency properties on the control itself in the code-behind and then bind to those from the XAML. For example, you can create dependency properties for the various lists you have like this:
public static readonly DependencyProperty List1Property = DependencyProperty.Register(
"List1",
typeof(IList<string>),
typeof(MyControl));
public static readonly DependencyProperty List2Property = DependencyProperty.Register(
"List2",
typeof(IList<string>),
typeof(MyControl));
Then you can bind the ItemsSource property of your ItemsControls:
<ItemsControl ItemsPanel="..." ItemsSource="{Binding ElementName=root, Path=List1}" />
<ItemsControl ItemsPanel="..." ItemsSource="{Binding ElementName=root, Path=List2}" />
(in this case I assume that the custom control has a x:Name="root")
I hope this helps!
You can't bind the contents of a StackPanel directly. It's simply a layout control.
What you could do, however, is use a ListBox and set its ItemsPanel to be a StackPanel (or whatever other layout control you need). Then you can set the ListBox's ItemsSource to whatever underlying collection you want.
I have a Shell.xaml file which contains two other UserControls. On the left is my TreeView and on the right is a detail screen.
I want the detailscreen to be switchable based on a selected TreeViewItem. I know this can be achieved by using DataTemplates, because I've done it with simple button clicks and using the <ContentControl Content="{Binding CurrentDetailViewModel}"> tag to accomplish this, but I have no idea how to accomplish this based on a selected TreeViewItem. I also have a separate ViewModel class for my UserControl which holds my TreeView and a separate for each detail screen.
I've been using Josh Smith's tutorial on TreeViews: http://www.codeproject.com/KB/WPF/TreeViewWithViewModel.aspx
So I also do use the TreeViewItemViewModel.cs class of his.
Could someone shed some light onto this?
Thanks,
Grant
If both the treeview and the details are displaying the same object (i.e the ItemsSource of the treeview contains the objects that you want to data template in the custom control) then you should be able to set a property on an underlying ViewModel that both controls share and have the custom control display something relevant with data templates.
for example, in the ViewModel:
object TreeViewSelectedItem
{
get{ return _treeViewSelectedItem;}
set {_treeViewSelectedItem = value; NotifyPropertyChanged("TreeViewSelectedItem");}
}
Treeview xaml
<TreeView ... SelectedItem={Binding TreeViewSelectedItem Mode=OneWayToSource}".../>
custom control xaml
<UserControl>
<Control.Resources>
<DataTemplate DataType="{x:Type Plane}">
....
</DataTemplate>
<DataTemplate DataType="{x:Type Train}">
....
</DataTemplate>
<DataTemplate DataType="{x:Type Automobile}">
....
</DataTemplate>
</Control.Resources>
<ContentControl Content={Binding TreeViewSelectedItem}"/>
</Usercontrol>
What is the simplest example of binding the items of a TabControl to an ObservableCollection?
Each tab's content will have unique data, and indeed this data will have observableCollections of its own bound to the items components.
Currently I have a user control, which I would like to set as the content of each tab as soon as it is created. I also need to dynamically set the datacontext of this new user control when the tab is created. So, essentially, I would like the tabcontrol's observablecollection contain modelviews that map to the data in each tab.
On top of that, I need to do all this without violating MVVM in WPF! Any help?
Much appreciated!
Basic example :
<Window.Resources>
<DataTemplate x:Key="templateForTheContent" DataType="{x:Type vm:TheViewModelType}">
<v:YourUserControl/>
</DataTemplate>
<DataTemplate x:Key="templateForTheHeader" DataType="{x:Type vm:TheViewModelType}">
<TextBlock Text="{Binding ThePropertyToDisplayInTheHeader}"/>
</DataTemplate>
</Window.Resources>
...
<TabControl ItemsSource="{Binding YourCollection}"
ContentTemplate="{StaticResource templateForTheContent}"
ItemTemplate="{StaticResource templateForTheHeader}">
</TabControl>